Combustion control based on a signal from an engine vibration sensor

Abstract

Feedback control of an internal combustion engine is performed based on a signal from a vibration sensor and a crankshaft angle sensor. An energy factor can be computed based on these sensor signals. A vector of energy factor can be computed as a function of crank angle degree over a particular window of engine rotation of interest. Based on the energy factor vector, combustion phasing can be estimated.

1. An internal combustion engine, comprising:
 an accelerometer affixed to the engine; 
 an engine rotation sensor proximate the engine; and 
 an electronic control unit electronically coupled to the engine and said accelerometer, said electronic control unit adjusting engine parameters based on signals from said accelerometer and said engine rotation sensor, said signals being used to estimate combustion phasing, wherein said engine parameters are at least one of injection timing and EGR rate, the engine having an EGR system which comprises a duct connecting an engine intake with an engine exhaust via an EGR valve, the engine also having one fuel injector per engine cylinder. 
 
     
     
       2. The engine of  claim 1  wherein said engine has multiple accelerometers and signals from more than one accelerometer are averaged to compute combustion phasing in an engine cylinder. 
     
     
       3. The engine of  claim 2  wherein said signal from said accelerometer is windowed to provide a dataset over a desired interval of engine rotation roughly corresponding with combustion in a particular engine cylinder. 
     
     
       4. The engine of  claim 2  wherein said accelerometer signal is digitally acquired and filtered in said electronic control unit. 
     
     
       5. The engine of  claim 1  wherein said combustion phasing is determined based on applying a function to said signal and integrating said accelerometer signal. 
     
     
       6. The engine of  claim 5  wherein a combustion intensity is determined based on said combustion phasing. 
     
     
       7. The engine of  claim 6  wherein said combustion intensity is based on a number of crank angle degrees for the major portion of the combustion event to occur. 
     
     
       8. The engine of  claim 6  wherein said combustion intensity is based on a number of crank angle degrees between the 10% and 90% combustion times. 
     
     
       9. The engine of  claim 5  wherein said function comprises one of: squaring, cubing, and taking the fourth power. 
     
     
       10. A method for controlling an internal combustion engine, comprising:
 estimating combustion phase based on a signal from a vibration sensor coupled to the engine, said sensor detecting engine vibrations; and 
 adjusting an engine parameter based on said estimated combustion phase. 
 
     
     
       11. The method of  claim 10  wherein said engine parameter is one of: number of injections per power stroke, injection timing, EGR rate, boost pressure, amount of fuel inducted, and injection rate. 
     
     
       12. The method of  claim 10  wherein said internal combustion engine is a compression ignition engine. 
     
     
       13. The method of  claim 10  wherein said engine parameter is one of: spark timing, injection timing, EGR rate, boost pressure, air-fuel ratio, and injection rate. 
     
     
       14. The method of  claim 13  wherein said internal combustion engine is a spark ignition engine and said method is applied when said engine is undergoing non-knocking combustion. 
     
     
       15. The method of  claim 10  wherein said sensor is an accelerometer affixed to the engine. 
     
     
       16. The method of  claim 10 , further comprising:
 acquiring a voltage or charge signal from said vibration sensor multiple times during a window of engine rotation. 
 
     
     
       17. The method of  claim 16 , further comprising:
 adjusting a level of said acquired signal so that the mean value of the acquired signal values is zero. 
 
     
     
       18. The method of  claim 17 , further comprising:
 filtering said adjusted, acquired signal values with a bandpass filter. 
 
     
     
       19. The method of  claim 18  wherein said bandpass filter has calibratable upper and lower frequency limits. 
     
     
       20. The method of  claim 19 , further comprising: rectifying said signal values when said power is odd. 
     
     
       21. The method of  claim 18 , further comprising:
 raising said filtered, adjusted, acquired signal values to a predetermined power to obtain unfiltered energy factor values. 
 
     
     
       22. The method of  claim 18  wherein said predetermined power is 1, 2, 3, or 4. 
     
     
       23. The method of  claim 10 , further comprising:
 filtering said unfiltered energy factor values with a lowpass filter, said lowpass filter being calibratable. 
 
     
     
       24. The method of  claim 23  wherein said lowpass and bandpass filters is run in one of a forward and a forward-backward mode. 
     
     
       25. The method of  claim 23 , further comprising:
 summing said filtered energy factor values to obtain an energy vector. 
 
     
     
       26. The method of  claim 25 , further comprising:
 determining a crank angle, θp, at which p % of the maximum energy factor value has been obtained by finding θp which most closely satisfies:
     E   θp = p·E   θn   
 
 
       where E θn  is the maximum energy factor value and E θp  is the energy factor value at θp. 
     
     
       27. The method of  claim 26 , further comprising:
 estimating mass fraction burned crank angle based on the energy factor vector and engine rpm. 
 
     
     
       28. A method for controlling an internal combustion engine, comprising:
 estimating combustion phase based on an energy factor, said energy factor being based on the absolute value of the power of one, two, three, or four of a signal from a vibration sensor coupled to the engine, said sensor used for detecting engine vibrations during a portion of engine rotation which corresponds roughly when combustion is occurring in one of the engine's cylinders. 
 
     
     
       29. The method of  claim 28  wherein said vibration sensor signal is bandpass filtered with calibratable upper and lower limits, said bandpass filtering occurring prior to raising to said power of said sensor signal. 
     
     
       30. The method of  claim 29  wherein said calibratable upper and lower limits are based on at least one of engine architecture and engine operating conditions. 
     
     
       31. The method of  claim 28  wherein said power of said sensor signal is filtered in a lowpass filter which removes high frequency components, said lowpass filter cutoff being calibratable. 
     
     
       32. The method of  claim 28  wherein said power of said sensor signal is summed to provide an energy factor vector: 
       
         
           
             
               
                 
                   E 
                   → 
                 
                 0 
               
               = 
               
                 [ 
                 
                   
                     E 
                     
                       θ 
                       ⁢ 
                       
                           
                       
                       ⁢ 
                       0 
                     
                   
                   , 
                   
                     E 
                     
                       θ 
                       ⁢ 
                       
                           
                       
                       ⁢ 
                       1 
                     
                   
                   , 
                   
                     … 
                     ⁢ 
                     
                         
                     
                     ⁢ 
                     
                       E 
                       
                         θ 
                         ⁢ 
                         
                             
                         
                         ⁢ 
                         n 
                       
                     
                   
                 
                 ] 
               
             
           
         
         
           
             where 
           
         
         
           
             
               
                 E 
                 θ 
               
               = 
               
                 
                   ∑ 
                   
                     τ 
                     = 
                     
                       θ 
                       0 
                     
                   
                   θ 
                 
                 ⁢ 
                 
                     
                 
                 ⁢ 
                 
                   
                     
                       K 
                       2 
                     
                     ⁡ 
                     
                       ( 
                       τ 
                       ) 
                     
                   
                   ⁢ 
                   Δτ 
                 
               
             
           
         
       
       where K is the sensor signal as a function of crank angle, θ, and θ 0  is a starting crank angle for the computation. 
     
     
       33. The method of  claim 32  wherein said energy factor vector is computed over a window of crankangle degrees from to θ 0  to θn, said θ 0  to θn being calibratable based on engine architecture and engine operating conditions.